Abstract:

Based on the combination of the second law of thermodynamics and thermo-economic principle with the asymptotic fouling model, the costobjective function and the optimal cleaning cycle of heat exchanger were formulated by introducing exergy transfer and heat transfer effectiveness for a heat exchanger subject to foulingThe results showed that the optimal cleaning cycle and the corresponding total cleaning cost determined by the second law of thermodynamics might be greater or smaller than those by the first law of thermodynamics, because exergy price was different from heat price more or lessIn the meantime, the optimal cleaning cycle, representing minimum cost of operation and maintenance of heat exchangers varied with flow patterns of heat exchanger, number of heat transfer units without fouling, the ratio of cold to hot fluids heat capacity, the cleaning time and the other cost parametersIn addition, the effect of the ratio of cold to hot fluids heat capacity and a smaller number of heat transfer units without fouling on the optimal cleaning cycle was not obvious as compared with other parameters.

Key words:

污垢, 换热器, 清洗周期, 热力学第二定律

摘要：

基于热力学第二定律和热经济学原理，通过引入换热器的传火用有效度和传热有效度以及污垢的渐近模型，研究换热器的最佳清洗周期，得到了换热器清洗时的总费用表达式。结果表明，基于热力学第二定律的最佳清洗周期和对应的清洗时的总费用与基于热力学第一定律结果的相对大小取决于火用价和热价的差异程度；最佳清洗周期受到换热器的流型、洁净状态下的传热单元数、冷热流体热容量比、清洗时间以及清洗过程损失费用等因素的影响，其中，冷热流体热容量比和较小的洁净状态下的传热单元数对最佳清洗周期的影响相对较小。

关键词:

污垢, 换热器, 清洗周期, 热力学第二定律